Electrical signaling system



Mmh 19, 1940.

.si L K 1NVENTOR- CHARLES EDMUND BEALE l ATTORNEY.

Patented Mar. 19, 1940 UNTED STATES ?ATENT OFFlCE signor to Associated Telephone & Telegraph Company, Chicago, Ill., a corporation of Dela- Application September 13, 1937, Serial No. 163,596 In Great Britain October 17, 1936 17 Claims.

The present invention relates to electrical signaling arrangements and is more particularly concerned with an improved method of signaling in response to the momentary reduction of an otherwise steady current flow in the signaling circuit. It has already been suggested in an arrangement of this character to employ as a responding device a relay specially constructed to have a very short release time so that it will respond to current changes of extremely small duration. The chief object of the invention is to obtain the same facilities by a suitable circuit arrangement of relays of the type ordinarily employed which are cheap to manufacture and do not require a critical adjustment to enable them to perform their functions satisfactorily.

According to the invention in an electrical signaling arrangement for effecting a switching opu eration in response to a signaling operation comprising the momentary opening of the signaling circuit and its subsequent completion by way of an impedance, a relay initially energised in a local circuit is maintained energised over the signaling circuit, the relay being wound and the spring tension adjusted so that reliable de-energisation will take place in response to a signaling operation of very short duration.

The invention is advantageously employed in telephone or like switching systems where it is desired to give an indication of the extension of a highly inductive circuit in which the electrical conditions after extension are not substantially changed but in which a momentary interruption of the current iiowing in this circuit occurs during the act of extension. The invention finds one useful application in the case of a telephone system employing register senders. By signaling to the register sender the instant at which a switch which has performed a hunting operation switches through to a succeeding switch, it is possible to arrange for the pause between successive trains of impulses transmitted by the register sender to be reduced to just the amount required and thus the operation of the system is speeded up.

Referring now to the accompanying drawing this shows sufficient of the circuits of a register sender of the type disclosed in British Patent No. 469,184 granted July 20, 1937 to Reginald Taylor and George Thomas Baker to enable the invention to be fully understood. The circuits are limited for the most part to an impulsev sending arrangement which is substantially unchanged from that of the before-mentioned patent except for the addition of relays P, Q and R. Shown schematically is the register K which in thewell known manner receives digits, stores them, and then in accordance with the value of the digits controls the transmission of trains of impulses by the impulse sender. The drawing also shows a train of switches X, Y and Z of the two motion i type. Such switches are completely disclosed in Patent No. 1,868,994 granted July 26, 1932 to Norman H. Saunders, and the present showing of them therefore includes only so much of the switches as is necessary to understand the invention.

The manner in which switches X, Y and Z function, while not new, will be reviewed briefly before explaining the operation of the impulse sender. When the impulsing loop circuit from the sender is completed to switch X (in any known way, this not being a part of the present invention) line relay A in the switch is energized over: earth, battery, the upper winding of relay A, contact hl, the negative side of the line, wiper S2 in 20 position l, the positive side of the line, Contact h2, the lower winding of relay A and earth. Relay A operates and energizes relay B in an obvious circuit extending over contact al; relay E operating prepares a testing circuit to wiper l?. As will be described presently relay A is then operated impulsively over the line and in the known way controls the stepping of the wipers of switch X to some level of its contact bank after which they are automatically rotated in search for an idle line in that level. During the impulsive operation of relay A, relay B remains operated by Virtue of being slugged or otherwise made slow to release. When the wipers nd an idle line, for example that leading to switch Y, relay H operates over: earth, Contact bl, the right hand Winding of relay H, contact b2, wiper?, contact IbI, resistance Wil, battery and earth. Relay H halts the hunting movement of the switch wipers and switches over contacts hl and h2, thereby extending the impulsing loop to line relay IA in switch Y which immediately energizes thereover. Relay IA upon operating closes contact Ial to energize relay IB. By the closure of contacts h3 and h4 upon operation of relay H, and the switch- 45 ing over oi contact IbI upon operation of relay IB, relay H is locked up over: earth, battery, the left hand Winding of relay H, contact h3, the right hand winding of relay H, Contact fill, wiper P, contact IbI and earth. Therefore when line relay A in switch X releases upon the switching over of contacts hI and h2 and thereby promotes the delayed release of relay B by opening contact aI, relay H does not release despite the opening of its original energizing circuit at contacts DI and b2. Relay IA is then operated impulsively over the line in the same manner as was relay A to cause the wipers of switch Y to search for an idle line in some desired level of its Contact bank, and when one is found, for example the line leading to switch Z, relay II-I energizes over: earth, contact Ib-I, the right hand winding oi relay IH, Contact i292, wiper P, Contact Zbl, resistance Wz'2, battery and earth. Relay IH switches the line through to relay 2A of switch Z by operation of contacts Ih! and |712, and closes'a locking circuit for itself at contacts lhs and lit, which locking circuit is completed at contact Zbl when relay 2B operates over Contact Zal responsive to the energization of relay 2A over the line loop. While in the drawing switch Z is the last switch to which the line loop is extended, i. a connector, it will be appreciated that without departing from the spirit of the invention there may be more than two selector switches such as X and Y through which the line is extended before reaching the connector. Also the invention is not intended tc be limited to the speciiic circuit details of selectors X and Y which are shown, these having been chosen merely to illustrate the manner in which switches of this type switch through each thereby disconnecting its own line relay and almost simultaneously connecting up the line relay oi a succeeding switch.

The general impulse sending arrangements of the known scheme will now be described briefly. When suiiicient digits have been received by the register (shown schematically as K in the drawing) for the destination of the call to be known, a start circuit is completed for the impulse sender by closure of contact st. In the sender. impulse springs IMPI and IMPZE are continuously operated at a speed of ten impulses per second, and springs IMPZ periodically short-circuit relay IG; consequently relay IG operates over: earth, start contact st in the register, contact 8e4, relay IG, resistance YN, battery and earth, only when the impulse springs IMP2 next open and remove the short-circuit. These springs are then connected to the magnet SM of the sender switch S by the switching over of contact igl, and this switch is stepped round at a speed of ten impulses a second over the following circuit: earth, contacts st, sell, IMPI! and igZ, magnet SM, battery and earth. When the sender switch reaches position 3, the short-circuit around impulse springs IMPI which previously extended over wiper S2 and contact se? is removed, and the outgoing loop circuit is completed from the negative lead, over impulse springs IMPI, contact sei. and wiper S2 to the positive lead; this circuit is interrupted periodically by impulse springs IMPI thereby to transmit a train of impulses to the rst selector X while impulse senders IMPZ continue to step the sender switch. The springs IMPI and IIVIPE it should be mentioned operate 180 out of phase with one another. After the required number of impulses in the rst train have been transmitted, relay SZ is operated by a marking placed upon bank S4 of the sender switch by register K, and this relay thereupon locks up to the sender switch homing bank S3 by closing contact 8e3. It also at armature seZ short-circuits the springs IMPI to prevent the transmission of further impulses, at armature sell releases relay IG and at armature S25 prepares a homing circuit for the sender switch. By the closing of contact igt upon release of relay IG the circuit: earth, wiper SI, contact ig3, interrupter contact sm of the magnet SM, magnet SM, battery and earth, is completed for advancing the sender switch by self-interrup tion until it reaches contact i5 whereupon relay IG is again operated over the circuit: earth, wiper SI in position l5, contacts S25, ql?, relay IG, resistance YN, battery and earth. The seliin terrupted circuit for the magnet SM is thereupon opened by Contact z'Q'S, and the sender switch is then advanced to contact I9 by impulses from the springs MM2 over the circuit: earth, wiper Si of the sender switch, contacts 325, q2, IMP2 and z'gI, magnet SM, battery and earth. Thereafter the sender switch is again advanced by selfinterruption over: earth, wiper SI, contacts ig3 and sm, magnet SM, battery and earth, and

when it reaches its home position relay SZ is released and the sending of the second series of impulses is initiated. The length of the interdigital pause is therefore determined primarily by the time taken for the sender switch. to step over contacts IE-i under the control of the springs IMPZ.

With the modied circuits according to the invention however, when relay SZ operates to termi'- nate the impulse train a circuit is completed over contacts sai and ri? for the lower winding of relay P and also the upper winding is inserted in the outgoing loop by the switching over of Contact sel?. Relay P is operated over its lower winding and at armature p2 energises relay R over: earth, contacts sel and p2. Relay R, by switching over armature r2 locks up independent of contact p2, and disconnects the lower winding of relay P. Relay P. is so adjusted that when it is once energised it will just hold operated by current flow through its upper winding over the outgoing loop, this winding being somewhat ineicient.

When the rst selector completes its hunting operation and switches through, the loop is momentarily opened by the operation of relay H and there is thus a momentary interruption in the current flow through relay P. Moreover, when armatures hl and h2 engage their front contacts the inductance of the de-energised line relay IA delays the rise of the loop current to its normal value. This reduction in the current through relay P is suflicient to cause its de-energisation. At armature pl the upper winding of relay P is short-circuited over Contact rI to prevent its re-operation when the loop current is restored, While at armature p2 a circuit is completed over: earth, contacts sel, p2 and r3, to operate relay Q. This relay locks up at armature qI and at armature q2 alters the stepping circuit for the sender switch magnet SM so that the switch is advanced over contacts IE-IE not under control of the impulse springs IMPZ as in the known scheme, but by self-interruption over the circuit: earth, wiper Si, contacts $25 and q2, interrupter contact sm, magnet SM, battery and earth. Consequently the sender switch is advanced to its home position more rapidly and on the release of relay SZ relays Q and R are released by the opening of contact sel; therefore the sending of the succeeding series of impulses is initiated after only the length of pause actually required rather than after a pause whose length is arbitrarily xed to a predetermined minimum by the comparatively slow stepping of the sending switch over contacts Ill-I8 under control of springs It will be appreciated that as an alternative to the arrangement for short-circuiting relay P upon its release as shown, the re-operation of outgoing loop circuit over its own operated contacts. Since the last switch of the train will ordinarily be the connector which responds to two digits, there will be no momentary signal sent back after the transmission of the penultimate digit and consequently in this case the register sender will give the full inter-digital pause since relay P will remain operated. Relay P is, of course, de-energised by the short-circuiting effect of armature sa?! when relay SZ falls aways. Similar considerations apply to the case where the call is extended to another exchange over a repeater though comparatively small changes would be necessary to enable the repeater to relay back the momentary signal.

It will be understood that the register sender may be provided in the usual manner with a polarised relay to hold up the sending beyond the normal interdigital pause in case a double or extended hunting operation is required between two successive switching stages.

I claim:

1. In a switching system, wherein the extension of a connection over an automatic switch may be controlled by transmitting impulses over a circuit extending to said switch, and wherein the extension of said connection is effective to transitorily interrupt said circuit, a relay in said circuit, and means for rendering said relay ineifective during said impulsing and for thereafter rendering said relay responsive to said transitory interruption of said circuit to indicate that said connection has been extended.

2. In a switching system, wherein an automatic switch having a control circuit extending thereto is adapted to signal revertively over said circuit responsive to the extension of a connection by said switch, means for signaling over said circuit to said switch thereby to control same to extend the connection, a relay, means for placing said relay under the control of said circuit upon completion of said last signaling, said relay thereafter responding to the signaling over said circuit by said switch to indicate when said connection is extended.

3. In a switching system, wherein connections are ext-ended progressively over a plurality of automatic switches, a control circuit, means for controlling each switch in turn over said circuit to extend said circuit to a succeeding one of said switches, a relay in said circuit, and means for rendering said relay inoperative during the controlling oi a switch and for thereafter rendering it responsive to the extension of said circuit from that switch to the succeeding switch.

4. In a switching system, a circuit extending to an automatic switch, a relay included in said circuit, another circuit for said relay, means for initially operating said relay in said other circuit and for holding it operated in said rst circuit, and means in said switch for extending said rst circuit through said switch, said relay responsive to said extension of said circuit through said switch to indicate that said circuit has been so extended.

5. In a switching system as claimed in claim 4, an impulse sender controlled by said relay to start transmitting impulses over said first circuit substantially immediately after the extension thereof through said switch.

6. In a switching system, a control circuit extending to an automatic switch, means for variably controlling said switch over said circuit to cause same to extend a connection, a relay, a first circuit for said relay including said controlling circuit, a second circuit for said relay,

and means for initially operating said relay over said second circuit and for holding it operated over said control circuit, said relay thereafter responsive to the extension of said connection.

7. In a switching system, a control circuit extending to an automatic switch, means for transmitting impulses over said control circuit to cause said switch to extend a connection, a relay in said circuit, said relay inoperative during said impulsing, another circuit for said relay, and means for transitorily energizing said relay in said other circuit after said impulsing has been completed to operate said relay and for causing it to be held operated over said control circuit, said relay thereafter responsive to the extension of said connection.

8. In a switching system, wherein connections are extended progressively over a plurality of automatic switches, a control circuit, means for transmitting impulses over said control circuit to each oi said switches in turn to cause that switch to extend said control circuit to a succeeding switch, a relay in said control circuit, a second circuit for said relay, means for initially operating said relay in said second circuit upon the termination of said transmission of impulses to a switch and for holding it operated in said conn trol circuit, said relay thereafter responsive to the extension of said control circuit to the succeeding switch.

9. In a switching system, a control circuit, a sender for transmitting trains of impulses over said control circuit, a relay in said circuit, another circuit for said relay, means effective upon termination of the transmission o a train of impulses to initially operate said relay in said other circuit and to thereafter hold said relay operated in said control circuit, and means for transitorily interrupting said circuit to release said relay, said relay effective upon its release to i control said sender to initiate the transmission of the next train of impulses.

1G. In a switching system, a control circuit, a sender for transmitting trains of impulses over said circuit to control automatic switches one after another to progressively extend said circuit, a relay, and means effective upon termination of the transmission of a train of impulses to a switch for placing said relay under control of said circuit, said relay thereafter responsive to the extension of said circuit from that switch to a succeeding one of said switches to thereby cause said sender to begin to transmit the next train of impulses to said succeeding switch substantially at once.

ll. A switching system as claimed in claim l0, wherein said sender includes means for introducing, between successive trains of impulses trans mitted over said circuit, a pause lasting a predetermined minimum length of time, and wherein said relay, responsive to the extension of said cir cuit through a switch before the expiry of said minimum length of time, renders said last means ineffective thereby to substantially eliminate the remainder of said pause.

l2. In a switching system, a control circuit, a sender for transmitting trains of impulses over said circuit to control automatic switches one after another to progressively extend said circuit, means in said sender for introducing a pause between successive impulse trains, a relay in said circuit, another circuit for said relay, and means effective upon termination of the transmission of a train of impulses to each switch for initially operating said relay in said other circuit and for holding it operated in said control circuit, the extension of said control circuit from that switch to a successive switch during a portion of said pause following said impulsing effective to release said relay to thereby cause the remainder of said pause to be substantially eliminated.

13. In a switching system, a control circuit, means for transmitting trains of impulses over said circuit to direct the progressive extension of a connection through automatic switches, a relay, a first circuit for said relay including said control circuit, means for rendering said rst circuit ineffective during the transmission of a train of impulses to a switch, a second circuit for said relay, means for rendering said rst and said second circuits effective, upon completion of said transmission of said train of impulses to said switch, to operate said relay, means for interrupting said second circuit and for thereafter holding said relay operated in said rst circuit, the eXtension of said connection from said switch to a successive switch effective to transitorily interrupt said control circuit and thereby release said relay, and means eiective upon release of said relay for rendering said rst circuit ineffective until transmission of the next train of impulses is initiated.

14. In a switching system having a pair of current feeding bridges of substantially the same potential, a circuit connected to one or" the bridges, change-over means for disconnecting said circuit from said one bridge and for at once connecting it to the other bridge, said bridges being so poled that current flows over said circuit in the same direction both before and after the operation of said change-over means, inductanoe included in said other bridge to delay the growth oi current supplied thereby to said circuit, whereby there is a transitory reduction in the value of the current ow over said circuit upon operation of said change-over means, and a relay connected in said circuit and actuated by said transitory reduction in the ow of current.

j l5.- Ina switching system having a pair of current feeding'bridges ofsubstantially the same potential, a relay, means for initially operating said relay, a circuit for said relay thereafter effective to maintain same operated from current supplied by one of said bridges, change-over means for disconnecting said one bridge from said circuit and for substantially simultaneously connecting thereto the other of said bridges, said other bridge being poled in the same direction as vsaid rst bridge but containing inductance to delay the growth of the current supplied to said circuit by said other bridge, whereby said relay is released by the transitory reduction in the value of current flow in said circuit responsive to the operation of said change-over means.

16. In a switching system as claimed in claim l5, means including a contact on said relay for short-circuiting said relay upon its release thereby to prevent reoperation of same following said transitory reduction in the value of current-flow in said circuit.

17. In a switching system having a pair of similar current feeding bridges, a circuit connected to one of said bridges, change-over means for dis connecting said circuit from said one bridge and for at once connecting it to the other bridge, said bridges being so poled that current flows over said circuit in the same direction both before and after the operation of said change-over means, a relay operated over said circuit responsive to the transitory interruption of current in said circuit upon operation of said change-over means, an impulse sender rendered effective bythe operation of said relay thereupon to interrupt said circuit one or more times in succession, and means for rendering said relay non-responsive to the interruption of said circuit by said impulse sender.

CHARLES EDMUND BEALE. 

